Process of producing stable hydrocarbon lubricants



Patented May 31, 1938 UNITED STATES PROCESS OF PRODUCING STABLE HYDRO- CARBON LUBRICANTS Ovid E. Roberts, .llr., New Rochelle, N. Y.

No Drawing. Application October a1, 1933, Serial No. 696,008

1 Claim. (01. lea-.29)

My invention relates generally to an improvement in processes of treatment of hydrocarbons of relativelyweakstructure to obtain hydrocarbons of more stable structure; and more particularly to the production of such structures within the range of lubricating oils.

My process has for its objects the production, from hydrocarbons of the class described, of refined products high in the desired qualities of purity, clarity and stability, and particularly the production of lubricants.

With the foregoing objects in view, and further objects as hereinafter more specifically stated, my invention consists in the treatment next to be described in detail.

I have found that hydrocarbons refined by the processes in general vogue in the oil industry are unsuited to many uses to which they are subjected, due primarily to the constitution of the hydrocarbons themselves, and to the failure of industrial practice to recognize the inherent Weaknesses of such structures. A sound practice must correct all structural weaknesses of these compounds under treatment in order to insure stability of product. a

It has long been recognized that any process of clarification, i. c. any method of producing a clear, light-colored product, improves the petroleum hydro-carbon under treatment. It has been :more recently recognized that saturation by such methods as hydrogenation produces a product of greater service and stability.

I have found that to produce a petroleum hydrocarbon of highest utility, it is essential to eliminate those compounds which tend to break down or react at. temperatures below, or at, those to which they are to be subjected; or, where elimination can be avoided, to effect their structural rearrangement in such a manner that the resulting compounds may assume a stability otherwise unattainable.

The elimination of sulfur compounds as a general class is highly desirable. Alcohols, aldehydes, amines, and the like, also constitute classes of compounds which readily break down, and by such decomposition are largely responsible for the deposition of large quantities of carbon within the engines in which the hydrocarbons may be intended to serve as a lubricant.

Where the hydrocarbon treated is in a distillation range characteristic of lubricants, these compounds are very largely unaffected by present refining practices.

Condensation by means of surfuric acid is not merely insuflicient but is very wasteful, as well as ineffective. It not merely Wastes many com.- pounds which are of real service value, but it is very indiscriminating in its general reaction tendencies. The same criticism holds true for the treatment with sodium and sodium-caustic so- 5 lutions and/or suspensions. Large percentages of additive compounds are lost Where such treatment is employed.

I have found that it is possible to treat hydrocarbons with highly desirable results by means of a Volatile ammonium salt, preferably in the vapor phase, and. thereby to produce effects not otherwise attainable.

An example of such a volatile ammonium salt is ammonium chloride. In cases Where the hydrocarbon treated is in the higher boiling range of the lubricants, such treatment may be carried on in vacuo.

The use of a volatile ammonium salt, such as ammonium chloride, produces a very desirable 20 series of reactions. It reacts with sulfur compounds such as mercaptans, thio-ethers, and the like, with the formation of complex polysulphides of unknown structure. These may be of a very high and complex structure and assume the na- 2 ture of tarry resins. In their formation they tend to adsorb, agglutinate or occlude the suspensoids in the hydrocarbon, and by their resultant re- 'moval of these impurities, are of real service and value in their clarifying effect. 30

I have found that at the temperatures attained in the course of such reaction, the ammonium ion exerts a far greater tendency to produce polymerization than sodium or potassiumeffects. At high temperatures, I find that the. value ofsodium or potassium is negligible as apolymerization agent, which is contrary to general assumption andbelief. This particularly holds true at temperatures over about 225 C. At these temperaturesI have found the alkali metals unusuaally reactive, showing marked tendencies to break down or crack the Weaker hydrocarbon structures and form high percentages of metallic salts of such high instability that the involved decomposition thereof is most wasteful. This decomposition must either be allowed to run its course to the ultimate destruction of the additive product or, by the removal of such products formed, account for a loss which is as unwarranted as it is unnecessary.

Such additive compounds as may result from the treatment of hydrocarbons by a volatile ammonium salt are stable and are within the desired range of marketable petroleum products. Where such reactivity has been great, the blend- 55 ing of a product so treated with another hydrocarbon otherwise treated, or of a lower reactivity similarly treated, may result in the production of a lubricant of exceptional qualities.

Many of the impurities of the hydrocarbons treated in the manner above described are watersoluble and may, by washing, be removed and recovered for such value as they may have in other fields. The use of a caustic or alkaline washing followed by fresh water treatment may also be desirable in certain instances. The exact final treatment, whether it includes drying, steam or vacuum distillation, will vary with the nature of the hydrocarbon so treated or the use for which it is intended.

The cost of such treatment will likewise vary with the nature of the hydrocarbon treated, as well as with the degree of refinement and stabilization desired. Without limiting myself in this matter, since the variation in the nature of hydrocarbons from different sources is great, I find that approximately two pounds of a volatile ammonium salt such as ammonium chloride per barrel may be required to treat a highly reactive heavy lubricant, whereas the treatment of a lower boiling hydrocarbon may require the use of substantially lower quantities of such a salt.

Where torrefaction or controlled and limited oxidation is desired in combination with the above described treatment, I use controlled amounts of ammonium nitrate suspended in pretreated stock, either molten or solid, and injected into the reaction zone in small controlled quantities. The feed supply of nitrate should be maintained throughout at a temperature not substantially exceeding 200 C. The entry of the nitrate-oil mixture as outlined, I have found, affords a reliable and economical means of promoting the controlled oxidation of the hydrocarbon under treatment. This is a very useful step in the treatment of any hydrocarbon designed for use as a lubricant, and is highly desirable for certain oils such as those used for transformer oils.

In the event that controlled oxidation is desired without the use of ammonium nitrate, I have found that the controlled injection of a small amount of warm air in conjunction with the injection of the volatile ammonium salt, may produce highly satisfactory results, particularly where the oxidation rate desired is of a low order.

I have found that the use of a volatile ammonium compound in treating hydrocarbons in the range of lubricating oils has unusual merit from the standpoint of its effects on that class of hydrocarbons known as waxes or jellies. Where an oil is so processed, the efiect appears to be a considerable alteration in the chain structure of these compounds, and a tendency, apparently through a type of polymerization, to form a more stable, possibly a cyclic structure. Whatever the explanation of the rearrangement or change may be, there is an appreciable diminution of the wax or jelly content, which is a highly desirable achievement.

After the treatment prescribed, I find that the reduction of suspensoids and the like induces a marked change in the character of the wax which is formed when the lubricant is subjected to a reduction in temperature. Such a treatment is usually employed preliminary to Wax removal by settling, filtration, centrifuging, etc. The conditions produced by the ammonium ion reaction induce the formation of wax in large, well-defined crystalline structure, which is a great aid to its removal, no matter which one of the usual procedures in vogue be employed. This assistance in removal takes not only the form of speeding up the separation of crystal from liquor, but also makes possiblea more complete separation of these two components, giving a wax product of more general uniformity as well as an oil of lower pour and cloud points.

By stabilization, as used herein, I mean the production of a product less likely to be aifected by light, heat, or other physical force. I have found that a hydrocarbon which is properly stabilized may be exposed to the suns rays daily for several years without appreciable darkening or other decolorizing, and without showing any tendency to develop objectionable odor. There are few, if any, petroleum hydrocarbons in the gasoline range which are marketed as gasolene which will meet this test of stability.

As an example of a volatile ammonium compound alfording the desired ammonium ion, I have named ammonium chloride, as this is the preferential salt because of its functional efficiency and low cost. While other volatile ammonium salts, such as ammonium iodide, are usable, their use is not economical.

Where ammonium salts are utilized in the treatment of a hydrocarbon containing sulfur, the formation of ammonium sulphide may be used advantageously not only as a means of improving the quality of the hydrocarbon under treatment, but by the subsequent recovery of the ammonium sulphide and its oxidation to the corresponding sulphates, as a product of value in the fertilizer and other industries.

Having thus described my invention, I claim:

The process of producing stable hydrocarbon lubricants which comprises subjecting a petroleum distillate boiling in lubricating range to limited oxidaton with ammonium nitrate and also reacting the said distillate with an ammonium halide in highly dispersed state and at a temperature above 225 C. and within the boiling range of lubricants.

OVID E. ROBERTS, JR. 

